Naproxen is a non-steroidal anti-inflammatory drug. It is a non-selective COX-1 and COX-2 inhibitor Mitchell et al (1993). what is naproxen Structurally, naproxen is a propionic acid-derived NSAID with a chiral center. The (+) form is the active isomer. It exhibits analgesic, anti-inflammatory and antipyretic effects in human clinical studies by Segre (1980), Roszkowski et al. (1973) and in animal models of inflammation. Along with all drugs in the NSAID class, naproxen has been associated with gastric irritation Bjarnason et al (1997), Garcia Rodriguez (1997). Naproxen is administered by the oral route in immediate-release and extended-release formulations. Time to reach maximum effect is 2-4 hours, works within 1 hour. Naproxen is approximately 99% bound to plasma proteins. Naproxen is metabolized by demethylation and undergoes phase II metabolism by glucuronide conjugation. There is very little naproxen in the urine. Urinary excretion is mainly metabolites.
Pharmacology and mechanism of action
Naproxen and other NSAIDs produce analgesic and anti-inflammatory effects by inhibiting the synthesis of prostaglandins. The enzyme that NSAIDs inhibit is cyclooxygenase (COX). COX enzymes exist in two isoforms: COX-1 and COX-2. COX-1 is primarily responsible for the synthesis of prostaglandins, which are important for maintaining a healthy gastrointestinal tract, kidney function, platelet function, and other normal functions. COX-2 is induced and is responsible for the synthesis of prostaglandins, important mediators of pain, inflammation and fever. However, mediators derived from these isoforms have overlapping functions. Naproxen is a nonselective inhibitor of COX-1 and COX-2. The pharmacokinetics of naproxen in dogs and horses are quite different from those in humans. The human half-life is about 12-15 hours, the dog half-life is 35-74 hours, and the horse half-life is only 4-8 hours, which may lead to poisoning in dogs and transient effects in horses.